Alicyclic ketoesters and process for their manufacture



United States Patent 3,158,644 ALICYCLIC KETQESTERS AND PRGCESS F63 THEE MANUFACTURE Edouard Demole, Geneva, Switzerland, and Edgar Lederer, Sceaux, France, assignors to Firmenich & Cie, Geneva, Switzerland No Drawing. Filed Feb. 24, 196i, Ser. No. 91,334 Claims priority, application swimerland, Feb. 25, 1960, 2,121/60; July 27, 1960, 8,563/60 7 Claims. (Cl. 260-468) The present invention relates to new alicyclic ketcesters, more particularly to lower alkyl esters of 2-alkyl-3- oxo-cycloalkyl-acetic acids, which possess interesting olfactive properties and which, therefore, are useful in the preparation of a great variety of perfume compositions. The invention also relates to perfume compositions including said new alicyclic keto-esters.

The compounds of this invention can be represented by the following general formula wherein n represents an integer from 1 to 2, R represents an alkyl radical having from 4 to 6 carbon atoms and R represents methyl or ethyl.

The substituent represented by R in the above Formula I can be a straight chain alkyl radical such as n-butyl, n-pentyl or n-hexyl, or a branched alkyl radical, i.e. a secondary or tertiary alkyl radical, in particular an isoalkyl radical (having the terminal group CH(CH e.g. isobutyl, isopentyl, or (3-methyl-butyl) and isohexyl.

A sub-class of compounds of this invention includes those keto-esters of Formula I wherein n is 1, R is an alkyl radical having from 4 to 6 carbon atoms, and R is methyl or ethyl. Preferred members of this sub-class are the keto-esters wherein R is an alkyl radical having 5 carbon atoms, e.g. methyl Z-n-pentyl-3oXo-cyclopentylacetate, ethyl 2-n-pentyl-3-0X0-cyclopentyl-acetate, methyl Z-isopenty1-3-oxo-cyclopentyl-acetate, and ethyl 2-isopentyl-3- oxo-cyclopentyl acetate.

A further sub-class of compounds of this invention includes those keto-esters of Formula I wherein n is 2, R is an alkyl radical having from 4 to 6 carbon atoms, and R is methyl or ethyl. Preferred members of this sub-class are the keto-esters wherein R is an alkyl radical having 5 carbon atoms, e.g. the methyl and ethyl esters of 2-n-pentyl-3-oXo-cycloheXyl-acetic acid and 2-isopentyl-3-oxo-cycloheXyl-acetic acid.

The compounds of this invention have two asymmetric carbon atoms in the cycloalkyl ring and can, therefore, exist in two stereoisomeric forms which, however possess substantially the same olfactive properties.

The keto-esters (represented by Formula I) of this invention can be prepared by condensing a 2-alkyl-2- cycloalkene-l-one wherein the alkyl radical in the 2-position contains from 4 to 6 carbon atoms and the cycloalkyl nucleus has from 5 to 6 members, with a lower alkyl malonate in the presence of a basic condensing catalyst, sa ponifying and decarboxylating the resulting lower alkyl 2-alkyl-3-oXo-cycloalkyl-malonate and esterifying the 2- alkyl-3-oxo-cycloalkyl-acetic acid thus obtained in order to form the desired lower alkyl 2 alkyl-3-oxo-cycloalkylacetate. I i

This synthesis can be represented by the following reaction scheme:

((l3H2)nOH 000R H2O CR H3O fill C O 0 R 0 basic condensing agent saponitication decarboxylation acid medium lesterification The symbols n, R and R have the meaning defined above, and R represents a lower alkyl radical such as methyl and ethyl.

Part of the starting cycloalkenones used for carrying out this process are known compounds. As far as they are new compounds, known methods can be used for their preparation, e.g. the methods of PLA. Plattner & A.St. Pfau, Helv. Chim. Acta 20, 1474, (1937); T.M. Jacob, S. Dev, .1. Indian Chem. Soc. 36, 429 (1959); R.L. Frank et al., J. Am. Chem. Soc. 70, 1379 (1948); M.F. Ansell, SS. Brown, J. Chem. Soc. 1958, 2955; M.F. Ansell & J.W. Ducker, J. Chem. Soc. 1959, 329; E.W. Warnhoff & W.S. Johnson, J. Am. Chem. Soc. 75, 494, (1953); and C. Rai & S. Dev, Experientia 11, 114 (1955). Thus, 2- n-butyl-Z-cyclopentene-l-one, Z-n-hexyl-2-cyclopentene-1- one and 2-(3-methylbutyl)-2-cyclopentene-1-one can be prepared according to the method of Ansell and Ducker (10c. cit.) modified by Rai and Dev (loc. cit.) by reacting an enol ether of cyclopentane-1,2-dione with an n-butyl-, n-hexylor S-methyl-butyl-magnesium halide, respectively, decomposing the resulting organo-magnesium compounds and treating the crude cycloalkenones thus obtained with hot polyphosphoric acid in order to isomerize small quantities or" isomeric cycloalkenones which normally contaminate the main reaction product. 2-n-hexyl-2- cyclopentene-l-one can also be obtained according to the method of Warnhoff & Johnson (loc. cit.) by selective chlorination of Z-n-hexyl-cyclopentane-l-one, deshydrochlorination of the chlorination product in collidine at C. and treatment of the crude reaction product with polyphosphoric acid. 2-n-amyl-2-cyclopentene-l-one can be prepared by cyclodeshydra-ting 'y-decalactone, with polyphosphoric acid according to the method of Pfau &

Plattner (loc. cit.) modified by Rai 8: Dev (loc. cit).

zinc and potassium iodide. Thus, e.g. Z-n-butyl-Z-cyclo hexene-l-one, 2-n-pentyl-2-cyclo-hexene-l-one, 2-isopentyl-2-cyclohexene-1-one and Z-n-hexyl 2 cyclohexene-lone can be prepared by this method from ethyl E-oxodecanoate, e-oxo-undecanoate, 5-oxo-9-methyl-decanoate and e-oxo-dodecanoate, respectively. The ethyl S-oxo- 9-methyl-decanoate is obtained by esterifioation of the corresponding acid which in turn is prepared by condensing isohexyl-methyl-ketone with di-ethyl carbonate in the presence of an alkaline condensing agent, condensing the resulting ethyl ,G-oxo-7-methyl-octanoate with methyl acrylate in the presence of NaOH to form methyl y-carbcthoxy-5-oxo-9-rnethyl-decanoate, and saponifying and decarboxylating the latter in order to obtain the desired 6-oxo-9-methyldecanoic acid.

The condensation of the starting 2-alkyl-2-cycloalkenel-ones with (ii-lower alkyl malonates, preferably with diethyl malonate, is conveniently carried out in the presence of sodium ethoxide used as the basic condensing catalyst. A preferred mode of effecting the condensation consists in adding first the diethyl malonate and then the Z-alhyl- 2-cycloalkene-lone to a solution prepared by dissolving sodium in an excess of absolute ethanol and by refluxing the reaction mixture for a few hours, e.g. for about 3 hours, while agitating.

The saponification and the decarboxylation of the dilower alkyl 2-alkyl-3-oxo-cycloa. icyl-rnalonate obtained in the first step can be carried out by conventional methods, e.g. by treating the substituted malonate with a mixture of acetic acid and concentrated hydrochloric acid at reflux temperature for several hours, e.g. for about 8 to 14 hours.

The final esterification of the 2-alkyl-3-oxo-cycloall ylacetic acids obtained in the second step into their methyl or ethyl esters can be effected by conventional methods, e.g. by reacting the substituted acetic acid with diazomethane, if the methyl ester is to be obtained, or by reacting said acid with methanol or ethanol in the presence of an acid catalyst such as concentrated sulfuric acid.

The keto-esters of this invention possess characteristic odors which care somewhat stronger in the series of the methyl esters than in the series of the ethyl esters. The new compounds are valuable fragrance-modifying agents by means of which interesting new notes can be imparted to numerous floral type and fancy type perfume compositions. In particular, the compounds of this invention can be used for balancing, modifying, enhancing and making more natural the floral note of perfume compositions. The notes which can be obtained by the addition of the keto-esters to perfumes are generally of a floral, slightly fatty, mushroom-like and woody type. A particular advantage of the new compounds results from the fact that they do not interfere with the desired fragrance ofa given perfume type. With the keto-esters of this invention being used in perfume compositions it is furthermore possible to reduce somewhat the proportions of natural flower oils normally used in the preparation of high quality perfumes, without causing any loss in quality.

The keto-esters of the present invention can be used,

either individually or as mixtures of at least two of them, in proportions which vary within wide limits and depend on the particular type of perfume wanted. in many cases it is suflicient to. add quantities of 0.5 to 10%, frc quently even 0.5 to 3%, of the total weight of the perfume composition if the new compounds are used as modificators. However, it may be advantageous to add quantities exceeding 10%, particularly if the keto-ester or a mixture of keto-esters is to-be used as one of the main ingredients in a perfume composition.

Particularly interesting results are achieved'in the creation of fragrances by using the methyl and ethyl esters of Z-n-amyland 2-isoamyl-3-oxo cyclopentyl-acetic acids and the methyl ester of 2-n-amyl-3-oxo-cyclohexylacetic acid.

' Example 1 1.51 g. of sodium (0.0657 atom) and 100ml. of absolute ethanol are introduced into a three-neclt flask of 500 ml. provided with a stirrer, a reflux condenser and a thermometer, and protected from humidity by means of a calcium chloride tube. Thereafter, 52.5 g. (0.335 mole) of diethyl malonate and then 10 g. (0.0657 mole) of 2-namyl-Z-cyclopentene-l-one (prepared according to P1. A. Plattner 8: A. St. Pfau, Helv. Chim. Acta 20, 1474 [1937]; n =1.4713; d =0.9202) are introduced. The temperature of the contents of the flask is brought to 79 C. and then maintained between 74 and 76 C. for 3 hours. During this period the solution is vigorously agitated. It is then allowed to stand overnight. The solution is neutralized with acetic acid (about 4.2 g.) and the alcohol distilled off in a vacuum of 15 mm. The residue is extracted with ether. The ethereal solution is washed with a 5% solution of NaHCO and then twice with water. The ether is subsequently dried and distilled off. Finally the reaction product is distilled in a vacuum of 0.03 to 0.07 mm. Hg. There are thus obtained 17.39 g. of diethyl 2-n-amyl-3-oxo-cyclopentyl-malonate which distills between 120124 C. Yield: 84%, iZ =1.4579; d =1.042.

This substituted malonic ester is saponified and decarboxylated by refluxing it for 14 hours in a mixture of 138 ml. of acetic acid and 209 ml. of concentrated hydrochloric acid. Then the solution is diluted with water and thoroughly extracted with ether. The acid formed as a result of the saponiiication and decarboxylation is then extracted by means of a 5% solution of sodium carbonate. The ether extract contains 3.1 g. of a neutral portion consisting substantially of the unsaturated starting ketone. The alkaline extract and the washings are acidified by means of H 50, of 10% strength and the acidic portions are extracted with ether. The ethereal extract is washed and dried. After evaporation of the ether there are obtained 7.65 g. of 2-n-amyl-3-oxo-cyclopentyl-acetic acid.

The 7.65 g. of substituted acetic acid obtained as described above are added to a mixture of 150 ml. of methanol and 15 ml. of concentrated H The mixture is refluxed for 3 hours. The reaction mixture is poured into 450 ml. of water and extracted three times with ether. After washing with water, sodium carbonate solution and again with water, the ethereal extract is dried and the ether is evaporated. There are thus obtained 6.94 g. of methyl 2-n-amyl-3-oxo-cyclopentylacetate distilling over between 85 and C. at 0.01 mm. Hg. This product possesses the following properties: n =1.4589; d =1.003.

Analysis.CaJculated for (2 1-1 0 C=68.99%, Il=9.80%. Found: C=68.93%, H=9.91%.

The corresponding ethyl ester of 2-n-amyl-3-oxo-cyclopentyl-acetic acid is prepared exactly in the same manner as described in Example 1 except that ethanol is used in the final esterification step.

Example 2 By repeating the procedure described in Example 1 but starting from 38.03 g. of Z-n-butyl-Z-pentene-l-one (n =1.4720; d =0.9290), 6.32 g. of sodium, 400 ml. of ethanol and 220 g. of diethyl malonate, there are obtained 68.2 g. (83%) of diethyl 2-n-butyl-3-oxo-cyclopen-tyl-malonate (12 =1.4584; a 1.0524).

59.7 g. of the substituted malonate prepared as described above are saponified and decarboxylated in the manner described in Example 1. There are obtained 19.42 g. (49%) of 2-n-butyl-3-oxo-cyclopentyl-acetic acid.

14.13 g. of Z-n-butyl-3-oxo-cyclopentyl-acetic acid prepared as described above are esterified by means of 300 ml. of methanol and 30 ml. of cone. sulfuric acid in the manner described in Example 1. There are thus obtained 11.475 g. (76%) of methyl 2-n-butyl-3-oxo-cyclopentvl acetate 01 1.4569; d :101?) Analysis.-Calculated for C l-I G t Found: C=68.23 H=9.30.%.

5.29 g. of 2-n-butyl-3-oxo-cyclopentyl-acetic acid pre- C=68.99%, Found: C=68.98%, H=9.60%.

Example 3 7.29 g. (0.30 gram atom) of magnesium turnings and some iodine granules are placed in a flask equipped for a Grignard reaction. The flask is heated rather strongly in order to dry and activate the magnesium. The metal is covered with anhydrous ether, and a solution of 49.8 g. (0.33 mole) of isoamyl bromide in 75 ml. of the same solvent is introduced. The reaction is completed by re fluxing for 60 minutes.

A solution of 38.6 g. (0.25 mole) of cyclopentane-l,2- dione isobutyl enol ether in 330 ml. of anhydrous ether is added to the solution of the Grignard reagent at such a rate that the heat of the reaction maintains the mixture at reflux temperature. The reaction is completed by agitating the reaction mixture at room temperature for 60 minutes. The reaction mixture is poured into an icecooled solution of ammonium sulfate, and 150 ml. of HCl are added. The mixture is heated for 5 minutes at 25-30" C., cooled and extracted twice with ether. The organic phase is Washed twice with 5% NaHCO and three times With Water. The ethereal extract is dried over anhydrous sodium sulfate and concentrated on the water bath, whereupon the concentrate is distilled. The following fractions are recovered:

250 g. of polyphosphoric acid are heated at 100 C. with agitation. Fraction 2 (34.4 g.) is added to the hot polyphosphoric acid, and agitation is continued at the same temperature for to minutes. The mixture, while still hot, is poured into an excess of water and ice, and the mixture is extracted twice with ether. The organic phase is Washed three times with a saturated NaCl solution, twice with 5% NaHCO and again twice with a saturated NaCl solution. The ethereal extract is dried over anhydrous sodium sulfate and concentrated on a steam bath. The concentrate is then distilled. The following fractions are recovered:

Grams Fraction 1, B.P. .=501O0 C 0.6 Fraction 2, B.P. =100102 C. 21.7 Residue 7.8

Fraction 2 is the desired product, viz. 2-isoamyl-2- cyclopentene-l-one. The amount obtained corresponds to a yield of 57% based on the enol ether used for the Grignard reaction. After redistillation this ketone has the following characteristics: a

There are obtained 18.88 g. (51%) of 2-isoamy1-3-oxocyclopentyl-acetic acid.

' 13.91 g. of 2-isoamyl-3-oxo-cyclopentyl-acetic acid prepared as described above are esterified by means of 280 ml. of methanol and 28 ml. of conc. sulfuric acid in the manner described in Example 1. There are thus obtained 11.37 g. (76%) of methyl 2-isoamyl-3-oxo-cyclopentyl-acetate (n =1.4570; d =0.9972).

Analysis-Calculated for C H O C=68.99%, H=9.80%. Found: C=69.39%, H=9.52%.

4.974 g. of 2-isoamyl-3-oxo-cyclopentyl-acetic acid prepared as described above are esterified by means of 110 ml. of ethanol and 11 m1. of conc. sulfuric acid in the manner described in Example 1. There are thus obtained 4.091 g. (73%) of ethyl 2-isoamyl-3-oxo-cyclopentyl-acetate (n =1.4550; d =0.9809).

Analysis.-Calculated for C H O C=69.96%, H=10.07%. Found: C=70.50%, H=10.30%.

Example 4 By repeating the procedure described in Example 1 but starting from 22.82 g. of 2-n-hexyl-2-cyclopentene-1- one (n =1.4724; d =0.9127), 3.16 g. of sodium, 200 ml. of ethanol and 110 g. of diethyl malonate, there are obtained 37.4 g. (84%) of diethyl 2-n-hexyl-3-oxo-cyclopentyl-malonate (n =l.4589; d =l.0264).

Analysis.Calculated for (2 1-1 0 C=66.23%, H=9.26%. Found: C=66.01%, H=9.14%.

52.28 g. of diethyl 2-n-hexyl-3-oxo-cyclopentyl-malonate prepared as described above are saponified and decarboxylated in the manner described in Example 1. There are obtained 17.17 g. (47%) of 2-n-hexyl-3-oxocyclopentyl-acetic acid.

13.44 g. of 2-n-hexyl-3-oxo-cyclopentyl-acetic acid prepared as described above are esterified by means of 260 m1. of methanol and 26 ml. of conc. sulfuric acid in the manner described in Example 1. There are thus obtained 11.40 g. (80%) of methyl '2-n-hexyl-3-oxo-cyclopentyl-acet'ate (n =1.4575; d =0.'9865).

Analysis-Calculated for C I-1 03: C=69.96%, H=10.07%. Found: C=70.11%, H=9.84%.

3.73 g. of 2-n-hexyl-3-oxo-cyclopentyl-acetic acid prepared as described above are esterified by means of 80 ml. of ethanol and 8 ml. of conc. sulfuric acid in the manner described in Example 1. There are thus obtained 3.11 g. (74%) of ethyl 2-n-hexyl-3-oxo-cyclopentylacetate (n =1i4550; d =0.9707).

Analysis.-Calculated for C H O C=70.88%, H=10.30%. Found: C=70.98%, H 10.39%.

Example 5 A solution of g. (0.5 mole) of a-oxo-undecanoic acid in 800 ml. of absolute ethanol is mixed in a 5 literflask With a solution of 220 ml. of pure conc. sulfuric acid in 1400 ml. of absolute ethanol. The resulting solution is refluxed for 3 hours whereupon about 1000 ml. of the ethanol are distilled oil in vacuo. The concentrate is then poured into about 10 liters of cold water. The aqueous reaction mixture is extracted twice with ether and the combined ethereal extracts are washed once with water, six times with 5% sodium bicarbonate solution, three times with 10% sodium carbonate solution, and three times with water. After drying of the extract and evaporation of the ether the residue is distilled. The fraction (104.0 g.; 91%) distilling over between 81 and 85 C. (bath temperature: 123-135 C.) consists essentially of ethyl ii-oxo-undecanoate.

Analysis.Calculated for CHI-12403: C: 8 H=10.59%. Found: C=68.26%, H=10.59%.

15.73 g. (0. 68 gram atom) of sodium are powdered by means of 131 ml. of absolute xylene in a one-liter flask equipped with a stirrer, reflux condenser and dropping funnel. Then ml. of absolute benzene are added to the sodium suspension, the contents of the flask is heated to 75 C., whereupon the 104 g. (0.46 mole) of ethyl fi-oxo-undecanoate obtained in the manner described above are introduced Within 20 minutes. The reaction mixture is stirred for a further 6 hours at 8085 C. The reaction flask is cooled in ice water, and then 49 g. (0.82 mole) of acetic acid and finally 600 ml. of Water are added to the reaction mixture within amass-s I 15 minutes. The mixture is twice extracted with ether, and the combined ethereal extracts are washed twice with sodium bicarbonate solution, then with 5% sodium hydroxide solution until the acid portions are completely extracted, and finally with water until the washings are neutral. The combined alkaline washings are acidified with acetic acid, and a nitrogen current is passed through the solution in order to promote the crystallization of the reaction product. When the crystallization is completed (ice-box) the crystals are filtered oil and dried. There are thus obtained 64 g. (77%) of crystalline 2-n-amyl-cyclohexane-1,3-dione. This product is very unstable and is therefore used directly for the next reaction without any further purification.

The 64 g. of dione obtained in the manner described above are dissolved in 265 ml. of pure absolute chloroform in a one-liter flask equipped with a stirrer, a reflux condenser, a dropping funnel and protected from humidity by means of calcium chloride tubes. 19.3 g. (0.4 eq.) of phosphorus trichloride are introduced into the solution in the course of 5 minutes. The reaction mixture is stirred for a further 3 hours, while refluxing, and then concentrated to dryness in vacuo. The residue is taken up in water, and the solution is extracted twice with ether. The combined ethereal extracts are washed three times with 2% sodium hydroxide solution, twice with saturated sodium chloride solution and once with Water. The ethereal solution is first dried over Na SO and then over CaCI The ether is distilled off and the residue is then distilled in vacuo. The fractions distilling over between 55 and 67 C. (bath temperatures: 95-113" C.) at 0.001 mm. Hg. are combined and redistilled. There are thus obtained 52.022 g. of a fraction distilling between 59 and 64 C. (bath temperature: 95-105 C.) at 0.001 mm. Hg. (n =1.4975; d =l.0472) consisting essentially of 2n-amyl-3-chloro-2-cyclohexene-l-one. A medium fraction (61.561 C./-0.001 mm. Hg.) gives the following data on analysis.

Analysis.-Calculated for C H OCI: C=65.83%, H=8.54%, Cl=17.66%. Found: C=65.84%, H=8.40%, Cl=17.90%.

A mixture of 18.89 g. (94.1 millirnoles) of the chlorinated ketone prepared as described above, 23.94 g. (366 millimoles) of zinc activated by treatment with dilute hydrochloric acid, 14.7 g. of powdered potassium iodide and 65 ml. of ethanol is refluxed for 40 hours with occasional stirring of the reaction mixture. action mixture is concentrated to dryness, taken up in petroleum ether (boiling range: 3050 C.) and filtered. the filtering residue is washed several times with petroleum ether. The combined filtrates are washed once with hydrochloric acid, once with 5% hydrochloric acid, once with water, twice with 5% sodium bicarbonate solution and finally twice with Water. The petroleum ether solution is dried and the solvent evaporated whereupon the residue is distilled. There are thus obtained 11.858 g. (75.8%) of a fraction distilling between 105 and 108 C./9 mm. Hg and consisting essentially of 2-n-amyl-2- cyclohexene-l-one. A redistilled sample is used for analysis which gives the following values:

Calculated for C I-I 0: C=79.46%, H=10.92%. Found: C=79.36%, H=10.86%.

Then the rep 0.78 g. (0.034 gram atom) of sodium are dissolved in r 50 ml. of absolute ethanol. To the resulting solution there are added 27.3 g (170 millimoles) of freshly distilled di-ethyl malonate and 5.69 g. (34 millimoles) of 2-n-amyl-2-cyclohexene-i-one prepared as described above, and the mixture is refluxed for 3 hours. The reaction mixture is then allowed to stand overnight, then neutralized with acetic acid and concentrated under reduced pressure. The residue is taken up in Water and the solution extracted twice with ether. The ethereal extract is washed with; 5% sodium bicarbonate solution and then with'wa'ter, and finally dried. The residue obtained by evaporation of the ether is distilled at 0.01:mm. l g and a bath temperature of 169 C. There are thus ob- 8 tained 10.10 g. (91%) of diethyl 2-n-amyl-3-oxo-cyclohexyl-malonate of 13.1. 133 C./0.01 mm. Hg

A mixture of the 10.10 g. of diethyl 2-n-amyl-3-oxocyclohexyl-malonate prepared as described above, 70 ml. of acetic acid and ml. of cone. hydrochloric acid is refluxed for 12 hours. After cooling, the reaction mixture is poured into 500 ml. of water and twice extracted with ether. The acid ethereal extract is extracted with 5% sodium carbonate solution, washed with water, dried and concentrated. There are thus obtained 1.4 g. of neutral material. The alkaline extract is acidified with 10% sulfuric acid and then twice extracted with ether. The ethereal extract is worked up in conventional manner. There are obtained 6.0 g. (86%) of Z-n-amyl-3-oxocyclohexyl-acetic acid.

The resulting 6 g. of substituted acetic acid are dissolved in 45 ml. of absolute methanol, and the solution is added to a solution of 12 ml. of cone. sulfuric acid in 70 ml. of absolute methanol. The reaction solution is refluxed for 3 hours, then cooled and poured into 500 ml. of water. The mixture is twice extracted with ether. The combined ethereal extracts are washed with 5% sodium bicarbonate solution and with water, dried and concentrated. Distillation of the residue yields 5.192 g. (82%) of methyl 2-n-arnyl-3-oxo-cyclohexyl-acetate of B1. 8993 C./0.001 mm. Hg (bath temperature: 122- 133 C.; 11 1.4630; d =0.9979).

Analysis-Calculated for C H O C=69.69%, H: 10.07%. Found: C=70.11%,H=10.02%.

Further lower alkyl esters of Z-alkyl-3-oxo-cyclohexylacetic acids, e.g. the methyl and ethyl esters of 2-n-butyl- 3-oxo-cyc1ohexylacetic acid, 2-isoamyl-3-oxo-cyclohexylacetic acid and -2-n-hexyl-3-oxo-cyclohexyl-acetic acid, are obtained by exactly the same procedure as described in Example -5 but using as starting compounds the corresponding fi-oxo-alkanoic acids, e.g. 5- xo-decanoic acid, V

5-oxo-9-methyl-decanoic acid and a-oxo-dodecanoic acid, respectively.

The following examples illustrate the use of the new keto-esters in the preparation of perfume compositions.

Example 6 A chypre perfume composition is prepared by blending the ingredients listed below in the proportions set forth:

Ingredients: Parts by weight Gak moss absolute 6 Phenylethanol 12 Geraniol 6 Benzyl acetate 9 Linalool Q 6 Amylcinnamic aldehyde 4 7 Methyl 2-n-amyl-3-oxo-cyclopentyl-acetate 3 Styrallyl acetate 2 Vetiveryl acetate 9 Bergamot 9 Ylang-Ylang 3 Neroli bigarade 2 Methyl ionone 9 indoie, 10% in ethyl phthalate 2 1,1-dirnethyl-6-tert.-butyl-4 acetyl-indane (musky) 1 'y-Undecalactone, 10% in ethyl phthalate 2 Rose absolute 1 Jasmine absolute 2 Undecanal, 1% in ethyl phthalate 8 Dodecanal, 1% in ethyl phthalate 4 T his perfume composition has a better balanced fracyclopentyl-acetate can be replaced by the corresponding ethyl ester which, however, is conveniently added in somewhat higher proportions, e.g. of of the total weight of the perfume composition. The keto-ester included in the above formula can also be replaced by one of the other homologues, e.g. methyl or ethyl Z-iso-amyl- 3-oxo'cyclopentyl-acetate. Also mixtures of at least two of the keto-esters of this invention can be added depending on the particular note which is to be imparted to the perfume composition.

Example 7 A tuberose type of perfume composition is prepared by blending the ingredients listed below in the proportions set forth:

Ingredients: Parts by weight Amylcinnamic aldehyde 8 Benzyl salicylate 6 Linalyl cinnamate 10 Methyl benzoate 4 Benzyl benzoate 10 Benzyl acetate 6 Linalyl formate 3 Methyl anthranilate 3 Methyl 2-isoamyl-3-oxo-cyclopentyl-acetate 3 Indole, 10% in benzyl benzoate 3 Benzyl alcohol 18 Linalool 12 Nerol 6 Cinnamic alcohol 8 In the above formula the methyl 2-isoarnyl-3-oxo-cyclopentyl-acetate can be replaced by methyl 2-n-amyl-3-oxocyclohexyl-acetate which can be used in higher proportions, e.g. up to 10% of the weight of the perfume composition.

Example 8 A floral type of perfume composition is prepared by blending the ingredients listed below in the propontions set forth:

The particular ingredients and their proportions in the perfume compositions described in the above Examples are purely illustrative and are not to be construed as a limitation of the present invention. It will be apparent to those skilled in the art that the keto-esters of the invention can be used in widely varying proportions in the preparation of numerous other types of perfumes.

We claim:

1. A lower alkyl ester of a 2-alkyl-3-0xo-cycloalkylacetic acid wherein the ester lower alkyl has from 1 to 2 carbon atoms, the alkyl radical in the 2-position has from 4 to 6 carbon atoms, and the cycloalkyl nucleus has from 5 to 6 members.

2'. A lower alkyl ester of a 2-alkyl-3-oxo-cyclopen|tylacetic acid wherein the ester lower alkyl has from 1 to 2 carbon atoms and the alkyl in the 2-position has from 4 to 6 carbon atoms.

3. A lower alkyl ester of a 2-alkyl-3-oxo-cyclohexylacetic acid wherein the ester lower alkyl has from 1 to 2 carbon atoms and the alkyl in the 2-position has from 4 to 6 carbon atoms.

4. Methyl 2-n-amyl-3-oXo-cyclopentyl-acetate.

5. Methyl 2-(3-methyl-butyl) 3 0X0 cyclopentylacetate.

6. Ethyl 2-(3-methyl-butyl)-3-oxo-cyclopentylacetate.

7. Methyl 2-n-amyl-3-oxo-cyclohexyl-acetate.

References Cited in the file of this patent UNITED STATES PATENTS 2,015,239 Schrauth Sept. 24, 1935 2,265,437 Luthy et a1 Dec. 9, 1941 2,491,442 Coleman Dec. 13, 1949 2,992,269 Horrom et a1 July 11, 1961 FOREIGN PATENTS 449,211 Great Britain June 23, 1936 OTHER REFERENCES Ross: J. Chem. Soc. (London), vol. 127, pages 2358- 69 (1925).

Bartlett et al.: J. Am. Chem. Soc., 62, 2933-8 (1940).

Dernole et al.: Helvetica Chimica Acta, vol. 45, No. 2, (1962) pages 675-703. 

1. A LOWER ALKYL ESTER OF A 2-ALKYL-3-OXO-CYLCOALKYLACETIC ACID WHEREIN THE ESTER LOWER ALKYL HAS FROM 1 TO 2 CARBON ATOMS, THE ALKYL RADICAL IN THE 2-POSITION HAS FROM 4 TO 6 CARBON ATOMS, AND THE CYCLOALKYL NUCLEUS HAS FROM 5 TO 6 MEMBERS. 